Apple Store App

I have previously used the Apple Store App on my iPhone4s without any problems. But in the last week or so, when I have tried to reserve something. IE. Apple TV in store, all I get is an error message 'Unable to complete your request, please try later'.

I have three iPhone's on on my account, an iPhone4s, iPhone4 and a iPhone3GS. I get the same message on all iPhones!